This invention relates to new chemical materials having improved thermal stability under load, comprising a polyurethane ("PUR"), a fibrous reinforcing substance and a polar polymer based on olefinically unsaturated monomers.
It is known that glass fibers may be incorporated in a wide variety of thermoplasts, including thermoplastic polyurethanes ("TPU"). Products of this type, however, have insufficient impact strength in the cold when produced on the basis of a rigid polyurethane and insufficient green strength on removal from the mold and little tear strength when produced on the basis of flexible polyurethane.
It is also known that mixtures (so-called "blends") of thermoplasts containing TPU and ABS (acrylonitrile/butadiene/styrene) polymers may be produced, e.g. by coextrusion. The ABS polymer is generally prepared using ca. 30%, by weight, of butadiene (see g.g. U.S. Pat. No. 3,049,505). One disadvantage of these thermoplastic blends is the insufficient thermal stability under load thereof. Even at 80.degree. C., the material may no longer withstand relatively high loads. The impact strength of these blends at low temperatures is also only moderate and the abrasion resistance is poor. Molded articles obtained from these products cannot be stacked immediately after the removal thereof from the mold because they still have insufficient strength.
In German Offenlegungsschrift No. 2,014,385, there is described the reaction of copolymer latices based on butadiene, styrene, methacrylic acid, acrylonitrile, and the like, and containing reactive hydrogen atoms with polyisocyanates. The latex represents the continuous matrix of the finished material, which is not thermoplastic. In contrast to these materials, the products of the present invention, described below, have much greater strength and rigidity.
In German Offenlegungsschrift No. 2,627,073 there are claimed polyurethane dispersions in polyols, to which aqueous polymer latices may also be added. These dispersions serve as polyol components for the production of polyurethane materials. The products described in the examples cannot be worked thermoplastically. The same applies to U.S. Pat. No. 2,993,013.
Adhesives based on mixtures of polyurethane, styrene copolymers and ABS polymers are described in German Auslegeschrift No. 2,355,942. The presence of the styrene copolymers is essential for the adhesive action of these substances, but no mention is made in the publication of thermoplasts or the addition of glass fibers.
German Offenlegungsschrift No. 2,128,199 relates to copolymers which are prepared by the reaction of polyisocyanates with polyols in the presence of other thermoplasts. Some of these copolymers are not impact resistant (due to the addition of styrene) or they have only low mechanical strength characteristics. The thermal stability under load of these products is insufficient.
A thermoplastic material has now surprisingly been found, which combines very high mechanical strength, thermal stability under load even to temperatures over 110.degree. C. and in some cases up to 160.degree. C., with advantageously high impact strength at low temperatures. This material, which comprises thermoplastic polyurethane, glass fibers and polar polymer, may be shaped surprisingly well in the conventional processing machines for thermoplasts. The molded articles may be stacked and transported immediately after the formation thereof. They may easily be lacquered and show very good adherence of the lacquer. The impact strength in the cold at -30.degree. C. is very high in spite of the presence of glass fibers and the fact that the PUR matrix is, in part, already frozen at this temperature.